Skip Navigation Links 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center



Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/

Satellite and Radar Imagery
  GOES-East Satellite
  GOES-West Satellite
  National Radar
Product Archive
WPC Verification
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
WPC Overview
   About the WPC
   WPC History
   Other Sites
Meteorological Calculators
Contact Us
   About Our Site is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
Winter Weather Forecast Discussion
(Caution: Version displayed is not the latest version. - Issued 1939Z Sep 28, 2023)
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
Abbreviations and acronyms used in this product
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
339 PM EDT Thu Sep 28 2023

Valid 00Z Fri Sep 29 2023 - 00Z Mon Oct 02 2023

...Sierra Nevada and highest terrain of the Great Basin
Days 2-3...

A mid-level trough digging across the Pacific will sharpen as it
crosses into the Pacific Northwest Friday night, and then amplify
into a closed low over the Great Basin by Sunday morning. This
deepening trough is progged to feature 700-500mb height anomalies
falling to -3 standard deviations according to the NAEFS ensemble
tables, driving snow levels to as low as 8000 ft in the Sierra
D2-3, and to 9500-10000 ft across the Great Basin and Central
Rockies late in the forecast period. Forcing for ascent through
downstream divergence, height falls, and intensifying diffluence
within the LFQ of a jet streak rotating through the trough will
result in precipitation spreading across the area, which will fall
as moderate snow above these snow levels. WPC probabilities for
more than 4 inches peak high as 30% in the High Sierra (above 9000
ft) day 2.5 before waning the latter stages of D3. This will
likely produce at least minor impacts at the highest passes
including Tioga Pass. Additional very light snowfall accumulations
are possible above 10,000 ft in the Uintas on Sunday.

The probability of any ice accumulation across the CONUS is less
than 10 percent.